It will take an all day trip to do Victoria from Vancouver unless you take a Helicopter or plane. There are lots of things to do in Vancouver proper. Stanley Park, Capillano suspension bridge, Chinese garden in Chinatown, just to name a few. I am sure the Vancouver residents form the board could add a lot to this list.
You can definitely see Victoria (and Butchart Gardens) on a one day tour. Go to GrayLIne Tours : http://www.grayline.ca and look up Vancouver to find tours. It's a really nice tour. YOu get two ferry rides, the garden and Victoria's beautiful harbour.
If you want to get to a mountain, there's Whistler (world known) that is a great day trip as well - absolutely gorgeous there- or if that doesn't work - Grouse Mountain is about 15 minutes away from downtown - I believe short bus tours will go there and while you're in the area, you might want to visit the Capilano Suspension Bridge.